Removal of manufacturing residues, for example oil, grease or chips from workpieces which have fine structural features with bores, recesses, fissures and other openings, has until now essentially been performed using solvent-based cleaning methods. The solvents dissolve grease and oil residues, but also facilitate penetration of the cleaning fluid into very small capillary openings and fissures because of the small surface tension. Such cleaning methods, however, disadvantageously use chemical solvents which require a complex post-treatment or disposal of the cleaning fluid.
The known devices and methods for cleaning workpieces without using a solvent are inadequate for cleaning workpieces with filigree openings and surface structures.
A device and a method for cleaning workpieces which does not require a solvent, is known from DE 43 17 862 A1. Workpieces are here introduced in a wash tank which is then closed air-tight and a reduced pressure is generated in the tank. This reduced pressure causes liquid to be drawn into the wash tank through a pipe connection; subsequently air is blown into the liquid bath.
DE 92 17 047 U1 describes a device for cleaning workpieces wherein the workpieces are surrounded by a bath with a wash liquid into which a gaseous medium is blown under an excess pressure. A reduced pressure can be generated in an air space above the bath containing the wash liquid.
DE 37 02 675 A1 describes a device for wet cleaning workpieces wherein a turbulent flow is produced in a immersion bath using a liquid jet, wherein the workpieces to be cleaned are arranged in the immersion bath.
EP 0 507 294 A1 discloses a device for cleaning work pieces which includes a treatment vessel and a workpiece support arranged in the treatment vessel for receiving workpieces. A spray unit which is disposed in the treatment vessel and has discharge nozzles for discharging a cleaning fluid, is arranged so as to be rotatable above the work piece support. Also provided is a flooding pipe for entirely or partially flooding the cleaning vessel with a cleaning fluid. The device described above can be used to carry out a method for cleaning workpieces wherein the workpieces are cleaned using an immersion process by flooding the cleaning vessel or, alternatively, a spray process by applying to the work pieces a cleaning jet from a spray cleaning unit.
DE 44 46 587 A1 describes a cleaning device with a tank which can be used to clean a charge using a cleaning liquid supplied through nozzles of a supply line. A reduced pressure can be generated in the treatment vessel. A discharge pipe is located in the lower section of the treatment vessel, with the discharge pipe being either connected to the supply line via a circulation pump or via a pump to a storage tank, wherein the storage tank is in turn connected to the supply line via a pump.
The known devices and methods have the disadvantage of not being very effective for cleaning workpieces having small surface features and, in particular, for cleaning small workpieces which are introduced into the cleaning vessel in the form of loose parts.
It is therefore an object of the present invention to provide a device for cleaning workpieces which allows reliable cleaning of small workpieces and of workpieces having filigree surface structures. The device should also operate reliably when cleaning fluids that do not contain solvents are used, and should eliminate the disadvantages described above.
It is another object of the invention to provide a method for cleaning and drying workpieces which can be carried out using the device of the pr invention.